Inhalers are well known in the prior art. Various types exist. A first type of inhaler contains a reservoir receiving many doses of powder, the inhaler being provided with metering means making it possible, on each actuation, to remove one dose of said powder from the reservoir, so as to bring said dose into an expulsion duct in order to be dispensed to the user. Another type of inhaler consists in placing the doses of powder in individual predosed reservoirs, then in opening one of the reservoirs each time the inhaler is actuated. That implementation seals the powder more effectively since each dose is opened only when it is about to be expelled. In order to make such individual reservoirs, various techniques have already been proposed, such as an elongate blister strip or blisters disposed on a rotary circular disk. All existing types of inhalers, including those described above, present both advantages and drawbacks associated with their structures and with their types of operation. Thus, with certain inhalers, there is the problem of metering accuracy and reproducibility on each actuation. In addition, the effectiveness of the dispensing, i.e. the fraction of the dose that effectively penetrates into the user's lungs in order to have a beneficial therapeutic effect, is also a problem that exists with a certain number of inhalers. With regard to opening the individual reservoirs, it has been proposed to peel off or to unstick the closure layer. That presents the drawback of difficulty in controlling the forces to be applied in order to guarantee complete opening, without running the risk of opening the next reservoir, particularly if the opening means need to be actuated by inhalation. Another problem that exists with inhalers provided with blister strips is associated with the movement of the strip, and with storage of the used portion of the strip. Thus, depending on the length of the strip and/or the thickness of the blisters, a large amount of space can turn out to be necessary, and any blockage of the blister strip can prevent the inhaler from functioning properly. In addition, when the device for advancing the strip pulls simultaneously on the leading end of the strip so as to avoid poor rolling up, a problem can occur over successive actuations, in particular because the rolled-up diameter of the used strip increases progressively. Multidose inhalers and inhalers containing a blister strip are thus generally complex devices constituted by a large number of parts, and thus costly to manufacture and to assemble. In order to make devices less complex and thus less costly, inhalers have been proposed that include individual reservoirs, such as capsules, that are loaded into the inhaler just before said inhaler is used. The advantage of such devices is that it is not necessary to store all of the doses inside the appliance, such that said appliance can be compact. However, the inhaler is more difficult to use, since the user is obliged to load a capsule into the inhaler before each use. Furthermore, other drawbacks specific to such a capsule inhaler have appeared. Thus, such devices are generally constituted by two parts, one being provided with the mouthpiece. During manipulation of such devices, for opening the capsule and releasing the powder, or for ejecting the empty capsule after inhalation, the user's fingers generally come into contact with the mouthpiece, and this can present risks of contamination. In addition, in order to eject the empty capsule, the device must generally be disassembled, and this exposes the inside of the device to any external pollution, which might subsequently be transmitted to the user during a future inhalation. Furthermore, the body of such a capsule inhaler is generally transparent so as to enable the user to see inside the dispersion chamber, and thus know firstly that the dose of powder has been dispensed after use, and secondly if the empty capsule has been ejected. Unfortunately, such a transparent body creates certain specific drawbacks. Thus, after each actuation, a small amount of powder generally remains stuck to the walls of the dispersion chamber. Such residues, which are visible from the outside, in particular after several uses, make the device look relatively dirty in appearance, and this can sometimes make the user feel uncomfortable and no longer wish to use the inhaler. Furthermore, as a result of its transparency, such a transparent body enables all kinds of light to pass therethrough, and in particular ultraviolet (UV) rays that may spoil the powder contained in the dispersion chamber. Document WO 2010/062744 describes a container containing photosensitive compounds, the container comprising an inner body that is in contact with the photosensitive compounds, and an outer body that is provided with a window made of anti-UV material.